How ascorbate tunes the activity and substrate selectivity of Fe(II)-dependent dioxygenase superfamily enzymes

Abstract

Across all domains of life, Fe(II)- and 2-oxoglutarate(2-OG)-dependent dioxygenase (FODD) superfamily enzymes carry out pivotal oxidation reactions that underlie key biological processes ranging from hormone biosynthesis to oxygen sensing to DNA repair and RNA modification. This study combines enzymology and structural biology to elucidate a new mechanism of FODD regulation whereby cofactor ascorbate (vitamin C) concentrations tune both the activity and substrate selectivity of FODD enzymes involved in RNA demethylation, and for the first time reveals the structural basis for ascorbates interaction with the FODD superfamily active site. Because ascorbate concentrations vary by over 100-fold across different cell types and disease states, our mechanistic work demonstrates how ascorbate levels likely play a critical, but underappreciated role in regulating RNA modification across the epitranscriptome and, more broadly, in regulating diverse biological oxidation reactions across the cell and human diseases.